Self-aligning roller bearings are known for its ability to handle demanding applications where the loads are high and where shaft deflections also can be expected. In fact, by using rollers instead of balls, larger loads can be accommodated. Moreover, the self-aligning capability, i.e. the capability of the bearing's inner and outer rings to be relatively misaligned, protects the bearing from internal stresses caused by shaft deflections, and therefore the bearing's service life may not be negatively affected by such deflections.
There are different types of self-aligning roller bearings, where one of the most common types may be the spherical roller bearing which comprises two rows of symmetrical rollers, a common sphered outer ring raceway and two inner ring raceways inclined at an angle to the bearing axis. The center point of the sphere in the outer ring raceway is at the bearing axis. There are also other types of self-aligning roller bearings. Such other examples may be 1) the spherical roller bearing which has two rows of asymmetrical rollers and 2) the toroidal roller bearing which comprises one row of rollers and where the bearing can accommodate both shaft deflections and axial shaft displacements.
It is also known to provide self-aligning roller bearings with seals for sealing off the openings between the inner and the outer ring. Such seals may be provided on the outside of the axial side face of the bearing or they may be integrated such that the seal is located in-between the bearing's rings without extending axially outside the bearing's perimeter. An advantage with sealed bearings is that it prevents foreign matter from entering the bearing's inside, and also it may be used for accommodating lubricant, such as grease. The sealing function is generally provided by the use of a circumferentially extending sealing lip made of rubber, which is in contact with either the inner or the outer ring.
One example of a sealed self-aligning roller bearing can be found in U.S. Pat. No. 9,739,313 B2, which discloses a seal unit formed in a multiple piece manner, the seal unit including an at least part-ring shaped main element which is freely rotatable with respect to the bearing's inner and outer ring and at least one seal lip. The seal lip provides a sealing between any one of the bearing's rings and the main element. Hence, there will not be a friction-free rotation between the seal unit and the bearing's rings.
Even though the above example may provide an improved bearing comprising an integrated sealing, there is however still a strive in further developing self-aligning roller bearings for more demanding applications.